Method for manufacturing outer joint member of constant velocity universal joint and ultrasonic flaw detection-inspection method for a welded portion

ABSTRACT

A manufacturing method is used for an outer joint member of a constant velocity universal joint. The outer joint member includes a cup section having track grooves formed in its inner periphery, which are engageable with torque transmitting elements, and a shaft section formed at a bottom portion of the cup section. The manufacturing method includes welding the cup and shaft members by irradiating a beam to joining end portions of the cup and shaft members, causing an outer surface including the welded portion to be formed into a flat smooth surface by removal processing, irradiating ultrasonic waves to the flat smooth surface with one probe at an incident angle which prevents total reflection in a circumferential angle beam flaw detection method, and setting a focal point of the ultrasonic waves to positions from a surface to an inside of the welded portion, to thereby perform inspection.

TECHNICAL FIELD

The present invention relates to a manufacturing method for an outerjoint member of a constant velocity universal joint, and to anultrasonic flaw detection-inspection method for a welded portion.

BACKGROUND ART

In a constant velocity universal joint, which is used to construct apower transmission system for automobiles and various industrialmachines, two shafts on a driving side and a driven side are coupled toeach other to allow torque transmission therebetween, and rotationaltorque can be transmitted at a constant velocity even when the twoshafts form an operating angle. The constant velocity universal joint isroughly classified into a fixed type constant velocity universal jointthat allows only angular displacement, and a plunging type constantvelocity universal joint that allows both the angular displacement andaxial displacement. In a drive shaft configured to transmit power froman engine of an automobile to a driving wheel, for example, the plungingtype constant velocity universal joint is used on a differential side(inboard side), and the fixed type constant velocity universal joint isused on a driving wheel side (outboard side).

Irrespective of the plunging type and the fixed type, the constantvelocity universal joint mainly includes an outer joint member includinga cup section having track grooves formed in an inner peripheral surfacethereof and engageable with torque transmitting elements, and a shaftsection that extends from a bottom portion of the cup section in anaxial direction. In many cases, the outer joint member is constructed byintegrally forming the cup section and the shaft section by subjecting arod-like solid blank (bar material) to plastic working such as forgingand ironing or processing such as cutting work, heat treatment, andgrinding.

Incidentally, as the outer joint member, an outer joint member includinga long shaft section (long stem) may sometimes be used. In order toequalize lengths of a right intermediate shaft and a left intermediateshaft, the long stem is used for an outer joint member on the inboardside that corresponds to one side of the drive shaft. The long stem isrotatably supported by a rolling bearing. Although varied depending onvehicle types, the length of the long stem section is approximately from300 mm to 400 mm in general. In the outer joint member, the long shaftsection causes difficulty in integrally forming the cup section and theshaft section with high accuracy. Therefore, there has been proposed anouter joint member that is constructed by forming the cup section andthe shaft section as separate members and applying electron beam welding(Patent Document 1).

Defects such as blowholes and solidification cracks may occur in thewelded portion. Thus, a quality check by an ultrasonic flaw detectionmethod is generally performed. Internal defects can be inspected by theultrasonic flaw detection method. However, the ultrasonic flaw detectionmethod has a problem in that defects which occur in a range of fromabout 1 mm to 3 mm directly below a surface being affected by a surfacereflection echo cannot be detected. In general, such a non-detectableregion is referred to as “dead zone”. In Patent Document 2 and PatentDocument 3, there have been proposed methods of irradiating ultrasonicwaves obliquely in a circumferential direction with respect to a producthaving a columnar or cylindrical shape.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 2015-64101 A

Patent Document 2: JP 58-144742 A

Patent Document 3: JP 5-332996 A

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the manufacturing method for an outer joint memberdescribed in Patent Document 1, a joining end surface of the cup memberand a joining end surface of the shaft member are brought into abutmentagainst each other, and the cup member and the shaft member are weldedby irradiating a beam from an outer side to the abutment portion in aradial direction. Further, an outer diameter of the joining end surfaceis set to an equal dimension for each joint size. With thisconfiguration, there has been proposed an excellent manufacturing methodfor an outer joint member, which is capable of increasing the strengthof the welded portion and the quality, reducing the welding cost,enhancing productivity of the cup member and the shaft member, achievingthe cost reduction through the standardization of a product type of thecup member, and reduction of a burden of production management. However,no focus is given to improvement in inspection accuracy and ease ofinspection for the welded portion.

The ultrasonic flaw detection device described in Patent Document 2includes two or more fixed probes to irradiate ultrasonic waves from aplurality of different directions, and the inspection is performed whileconveying a workpiece by, for example, a conveyer in many cases.Further, there is difficulty in application to a product having acomplicated shape. Further, when an incident angle is set to 27° orless, the surface reflection echo is generated, with the result that thedead zone is formed. For example, in a case of butt-welding of acylindrical component such as an outer joint member of a constantvelocity universal joint having an outer diameter of φ100 mm or less,there is given a small welding depth of 7 mm or less, and hence there isrequired highly accurate detection of a welding defect of about 0.5 mmfor an entire region of the welded portion. The inspection range foreach workplace is small. Therefore, with the ultrasonic flaw detectiondevice including the above-mentioned conveyance device, the size of thefacility is increased, with the result that the equipment cost becomesmore expensive. Further, products have different shapes. Therefore,there is difficulty in application of a simple adjustment mechanismdescribed in Patent Document 2, with the result that labor is requiredfor adjustment of setups. Thus, it has been found that theabove-mentioned technology is not applicable at the level of enablingindustrial production of an outer joint member of a constant velocityuniversal joint being a mass-produced product for automobiles and thelike.

When the incident angle is set to from about 60° to about 70° as in thesurface defect detection method described in Patent Document 3, the deadzone is not formed. However, those are angles at which the ultrasonicwaves do not enter an inside (critical angles), with the result that aninspection range is limited to a small range in the surface.

Attempts to eliminate or reduce the dead zone in the vicinity of thesurface to inspect the entire region have been made, but there a case inwhich countermeasures cannot be applied due to limitation of a productshape or a problem of an inspection range.

The present invention has been proposed in view of the above-mentionedproblems, and has an object to provide a manufacturing method for anouter joint member, which enables defect detection for an entire regionof a welded portion, that is, a region of the welded portion from asurface to an inside, of an outer joint member of a constant velocityuniversal joint being a mass-produced product for automobiles and thelike with high detection accuracy and also at the level of enablingindustrial production, thereby being capable of increasing the strengthof the welded portion and the quality, enhancing productivity, andachieving reduction of the manufacturing cost, and to provide anultrasonic flaw detection-inspection method for a welded portion.

Solution to the Problems

As a result of various studies conducted to achieve the above-mentionedobject, the inventors of the present invention have arrived at thepresent invention with new idea of removing the welded portion to form aflat smooth surface and eliminate the dead zone in the vicinity of thesurface and performing inspection with one probe for an entire region ofthe welded portion, that is, a region of the welded portion from thesurface to an inside of the welded portion, at an incident angle whichprevents total reflection of the ultrasonic waves.

As a technical measure to achieve the above-mentioned object, accordingto one embodiment of the present invention, there is provided amanufacturing method for an outer joint member of a constant velocityuniversal joint, the outer joint member comprising a cup section havingtrack grooves formed in an inner periphery of the cup section, which areengageable with torque transmitting elements; and a shaft section formedat a bottom portion of the cup section, the outer joint member beingconstructed by forming the cup section and the shaft section as separatemembers, and by welding a cup member forming the cup section and a shaftmember forming the shaft section to each other, the manufacturing methodat least comprising: a welding step of welding the cup member and theshaft member by irradiating a beam to joining end portions of the cupmember and the shaft member; a removal processing step of causing anouter surface including a welded portion formed in the welding step tobe formed into a flat smooth surface by removal processing; and anultrasonic flaw detection-inspection step of irradiating ultrasonicwaves to the flat smooth surface with one probe at an incident anglewhich prevents total reflection of the ultrasonic waves in acircumferential angle beam flaw detection method, and setting a focalpoint of the ultrasonic waves of the probe to a plurality of positionsfrom a surface to an inside of the welded portion, to thereby performinspection.

Further, according to one embodiment of the present invention, there isprovided an ultrasonic flaw detection-inspection method for a weldedportion of an outer joint member of a constant velocity universal joint,the outer joint member comprising a cup section having track groovesformed in an inner periphery of the cup section, which are engageablewith torque transmitting elements; and a shaft section formed at abottom portion of the cup section, the outer joint member beingconstructed by forming the cup section and the shaft section as separatemembers, and by welding a cup member forming the cup section and a shaftmember forming the shaft section to each other, the ultrasonic flawdetection-inspection method comprising forming an outer surfacecomprising the welded portion into a flat smooth surface by removalprocessing; irradiating ultrasonic waves to the flat smooth surface withone probe at an incident angle which prevents total reflection of theultrasonic waves in a circumferential angle beam flaw detection method;and setting a focal point of the ultrasonic waves of the probe to aplurality of positions from a surface to an inside of the weldedportion, to thereby perform inspection.

The above-mentioned configuration enables achievement of themanufacturing method for an outer joint member and the ultrasonic flawdetection-inspection method for a welded portion, which enables defectdetection for the entire region of the welded portion, that is, theregion of the welded portion from the surface to the inside of the outerjoint member of the constant velocity universal joint being amass-produced product for automobiles and the like with high detectionaccuracy and also at the level of enabling industrial production,thereby being capable of increasing the strength of the welded portionand the quality, enhancing productivity, and achieving reduction of themanufacturing cost.

Specifically it is desired that the above-mentioned removal processingin the removal processing step comprise turning, and that, in theultrasonic flaw detection-inspection step, the ultrasonic waves beirradiated in a direction parallel to turning marks formed by theturning. With this configuration, the dead zone caused by the surfacereflection echo is prevented from being formed, thereby being capable ofachieving high detection accuracy.

It is desired that a surface roughness of an outer surface having beensubjected to the above-mentioned turning be set to Ra 2.0 or less. Withthis configuration, there is no influence of the surface roughness,thereby being capable of achieving high detection accuracy.

It is desired that the incident angle of the ultrasonic waves in theabove-mentioned ultrasonic flow detection-inspection step be set to from10° to 27°. With this configuration, formation of the dead zone in thevicinity of the surface is suppressed, thereby enabling irradiation ofthe ultrasonic waves to the inside.

It is desired that a position of the focal point of the ultrasonic wavesof the above-mentioned probe be controlled by a program. With thisconfiguration, the manufacturing method is applicable to a complicatedworkpiece (outer joint member) shape and an outer joint member assignedwith a different product number. At the same time, adjustment of setupsfor equipment can easily be performed, thereby being capable of securingrepeatability of inspection.

In the above-mentioned ultrasonic flaw detection-inspection step, aworkpiece formed by welding the cup member and the shaft member isrotated during inspection, thereby being capable of performinginspection for one rotation (360°) of the welded portion in a shortperiod of time.

In the above-mentioned ultrasonic flaw detection-inspection step, when afocal point of the ultrasonic waves of the probe is set to a pluralityof positions within the thickness of the welded portion, and the probescans a plurality of positions in the axial direction, the entire regionof the welded portion can be inspected with one probe with highdetection accuracy.

Effects of the Invention

With the manufacturing method for an outer joint member of a constantvelocity universal joint and the ultrasonic flaw detection-inspectionmethod for a welded portion according to the present invention, it ispossible to achieve the manufacturing method for an outer joint member,which enables defect detection for the entire region of the weldedportion, that is, the region of the welded portion from the surface tothe inside of the outer joint member of the constant velocity universaljoint being a mass-produced product for automobiles and the like withhigh detection accuracy and also at the level of enabling industrialproduction, thereby being capable of increasing the strength of thewelded portion and the quality, enhancing productivity, and achievingreduction of the manufacturing cost, and to achieve the ultrasonic flawdetection-inspection method for a welded portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view for illustrating the entire structure of a drive shaftusing an outer joint member manufactured based on a manufacturing methodaccording to a first embodiment of the present invention.

FIG. 2a is an enlarged partial vertical sectional view for illustratingthe outer joint member of FIG. 1.

FIG. 2b is an enlarged view of the portion A of FIG. 2 a.

FIG. 2c is an enlarged view for illustrating a shape of the portion A ofFIG. 2a before welding.

FIG. 3 is an illustration of an overview of manufacturing steps for theouter joint member of FIG. 1.

FIG. 4a is a vertical sectional view for illustrating a cup memberbefore welding and after turning.

FIG. 4b is a vertical sectional view for illustrating the cup memberbefore welding and after turning.

FIG. 5a is a front view for illustrating a shaft member before welding,which is a billet obtained by cutting a bar material.

FIG. 5b is a partial vertical sectional view for illustrating the shaftmember before welding and after forging.

FIG. 5c is a partial vertical sectional view for illustrating the shaftmember before welding and after turning and spline processing.

FIG. 6 is a view for illustrating an overview of a welding step.

FIG. 7 is a view for illustrating an overview of the welding step.

FIG. 8a is an enlarged illustration of the welded portion after thewelding step, and is a vertical sectional view for illustrating a stateafter the welding step.

FIG. 8b is an enlarged illustration of the welded portion after thewelding step, and is a vertical sectional view for illustrating a stateafter a removal processing step for an outer surface including thewelded portion.

FIG. 9 is a graph for showing detection results of a surface reflectionecho with various surface roughness.

FIG. 10 is a front view for illustrating an overview of an ultrasonicflaw detection-inspection apparatus.

FIG. 11 is a plan view for illustrating an overview of the ultrasonicflaw detection-inspection apparatus.

FIG. 12 is a right side view for illustrating an overview of theultrasonic flaw detection-inspection apparatus.

FIG. 13 is a right side view for illustrating an overview of theultrasonic flaw detection-inspection apparatus.

FIG. 14 is a plan view for illustrating an overview of the ultrasonicflaw detection-inspection apparatus.

FIG. 15 is a partial enlarged view as seen from a direction indicated bythe arrows of the line F-F of FIG. 14.

FIG. 16a is an illustration of a state in which a probe scans in anaxial direction, and is a vertical sectional view for illustrating astate in which the probe scans on the shaft member side of the weldedportion.

FIG. 16b is an illustration of a state in which the probe scans in theaxial direction, and is a vertical sectional view for illustrating astate in which the probe scans at the center of the welded portion inthe axial direction.

FIG. 16c is an illustration of a state in which the probe scans in theaxial direction, and is a vertical sectional view for illustrating astate in which the probe scans on the cup member side of the weldedportion.

FIG. 17a is an illustration of a state of inspection by thecircumferential angle beam flaw detection method, and is across-sectional view for illustrating a state in which a focal point ofthe ultrasonic waves is positioned on a radially inner side of thewelded portion.

FIG. 17b is an illustration of a state of inspection by thecircumferential angle beam flaw detection method, and is across-sectional view for illustrating a state in which the focal pointof the ultrasonic waves is positioned at the center of the weldedportion.

FIG. 17c is an illustration of a state of inspection by thecircumferential angle beam flaw detection method, and is across-sectional view for illustrating a state in which the focal pointof the ultrasonic waves is positioned on a radially outer side of thewelded portion.

FIG. 18 is a partial vertical sectional view for illustrating a state inwhich an entire region of the welded portion is inspected.

FIG. 19 is an explanatory graph for showing an overview of a qualitydetermination program for a detection result of a defect of a weldedportion.

FIG. 20 is an explanatory graph for showing an overview of the qualitydetermination program for a detection result of a defect of the weldedportion.

FIG. 21 is an explanatory graph for showing an overview of the qualitydetermination program for a detection result of a defect of the weldedportion.

FIG. 22 is a front view for illustrating a shaft member assigned with aproduct number different from that of the shaft member of FIG. 5 c.

FIG. 23 is a partial vertical sectional view for illustrating an outerjoint member that is manufactured using the shaft member of FIG. 22.

FIG. 24 is a diagram for illustrating an example of standardization of aproduct type of the cup member.

FIG. 25 is a partial vertical sectional view for illustrating a constantvelocity universal joint of a different type, which is manufacturedbased on the first embodiment.

FIG. 26a is a partial vertical sectional view for illustrating the outerjoint member of FIG. 25.

FIG. 26b is an enlarged view for illustrating a shape of the portion Aof FIG. 25a before welding.

FIG. 27 is an illustration of an overview of a manufacturing method foran outer joint member according to a second embodiment of the presentinvention.

FIG. 28 is an illustration of an overview of a manufacturing method foran outer joint member according to a third embodiment of the presentinvention.

EMBODIMENTS OF THE INVENTION

Now, description is made of embodiments of the present invention withreference to the drawings.

A manufacturing method for an outer joint member of a constant velocityuniversal joint according to a first embodiment of the present inventionis illustrated in FIG. 3 to FIG. 24. An outer joint member which ismanufactured based on the manufacturing method according to the firstembodiment and a constant velocity universal joint are illustrated inFIG. 1 and FIG. 2. First, the outer joint member and the constantvelocity universal joint are described with reference to FIG. 1 and FIG.2, and subsequently, the manufacturing method for an outer joint memberaccording to the first embodiment is described with reference to FIG. 3to FIG. 24.

FIG. 1 is a view for illustrating the entire structure of a drive shaft1 using an outer joint member 11 manufactured based on the manufacturingmethod according to the first embodiment. The drive shaft 1 mainlycomprises a plunging type constant velocity universal joint 10 arrangedon a differential side (right side of FIG. 1: hereinafter also referredto as “inboard side”), a fixed type constant velocity universal joint 20arranged on a driving wheel side (left side of FIG. 1: hereinafter alsoreferred to as “outboard side”), and an intermediate shaft 2 configuredto couple both the constant velocity universal joints 10 and 20 to eachother to allow torque transmission therebetween.

The plunging type constant velocity universal joint 10 illustrated inFIG. 1 is a so-called double-offset type constant velocity universaljoint (DOJ). The plunging type constant velocity universal joint 10comprises the outer joint member 11 comprising a cup section 12 and along shaft section (hereinafter referred to also as “long stem section”)13 that extends from a bottom portion of the cup section 12 in an axialdirection, an inner joint member 16 housed along an inner periphery ofthe cup section 12 of the outer joint member 11, balls 41 serving astorque transmitting elements that are arranged between track grooves 30and 40 of the outer joint member 11 and the inner joint member 16, and acage 44 having a spherical outer peripheral surface 45 and a sphericalinner peripheral surface 46 that are fitted to a cylindrical innerperipheral surface 42 of the outer joint member 11 and a spherical outerperipheral surface 43 of the inner joint member 16, respectively, andbeing configured to retain the balls 41. A curvature center O₁ of thespherical outer peripheral surface 45 and a curvature center O₂ of thespherical inner peripheral surface 46 of the cage 44 are offsetequidistantly from a joint center O toward opposite sides in the axialdirection.

An inner ring of a support bearing 6 is fixed to an outer peripheralsurface of the long stem section 13, and an outer ring of the supportbearing 6 is fixed to a transmission case with a bracket (not shown).The outer joint member 11 is supported by the support bearing 6 in afreely rotatable manner, and when the support bearing 6 as describedabove is provided, vibration of the outer joint member 11 during drivingor the like is prevented as much as possible.

The fixed type constant velocity universal joint 20 illustrated in FIG.1 is a so-called Rzeppa type constant velocity universal joint, andcomprises an outer joint member 21 comprising a bottomed cylindrical cupsection 21 a and a shaft section 21 b that extends from a bottom portionof the cup section 21 a in the axial direction, an inner joint member 22housed along an inner periphery of the cup section 21 a of the outerjoint member 21, balls 23 serving as torque transmitting elements thatare arranged between the cup section 21 a of the outer joint member 21and the inner joint member 22, and a cage 24, which is arranged betweenan inner peripheral surface of the cup section 21 a of the outer jointmember 21 and an outer peripheral surface of the inner joint member 22,and is configured to retain the balls 23. As the feed type constantvelocity universal joint 20, an undercut-free type constant velocityuniversal joint may sometimes be used.

The intermediate shaft 2 comprises splines 3 for torque transmission(including serrations; the same applies hereinafter) at outer diameterson both end portions thereof. The spline 3 on the inboard side isspline-fitted to a hole portion of the inner joint member 16 of theplunging type constant velocity universal joint 10. Thus, theintermediate shaft 2 and the inner joint member 16 of the plunging typeconstant velocity universal joint 10 are coupled, to each other to allowtorque transmission therebetween. Further, the spline 3 on the outboardside is spline-fitted to a hole portion of the inner joint member 22 ofthe fixed type constant velocity universal joint 2. Thus, theintermediate shaft 2 and the inner joint member 22 of the fixed typeconstant velocity universal joint 20 are coupled to each other to allowtorque transmission therebetween. Although the solid intermediate shaft2 is illustrated, a hollow intermediate shaft may be used instead.

Grease is sealed inside both the constant velocity universal joints 10and 20 as a lubricant. To prevent leakage of the grease to an outside ofthe joint or entry of a foreign matter from the outside of the jointbellows boots 4 and 5 are respectively mounted to a portion between theouter joint member 11 of the plunging type constant velocity universaljoint 10 and the intermediate shaft 2 and a portion between the outerjoint member 21 of the fixed type constant velocity universal joint 20and the intermediate shaft 2.

The outer joint member manufactured based on the manufacturing methodaccording to the first embodiment is described with reference to FIG. 2.FIG. 2 are enlarged views for illustrating the outer joint member 11.FIG. 2a is a partial vertical sectional view. FIG. 2b is an enlargedview of the portion A of FIG. 2a . FIG. 2c is a view for illustrating ashape before welding. The outer joint member 11 comprises the bottomedcylindrical cup section 12 that is opened at one end and has thecylindrical inner peripheral surface 42 and the plurality of trackgrooves 30, on which the balls 41 (see FIG. 1) are caused to roll,formed equiangularly on the inner peripheral surface, and the long stemsection 13 that extends from the bottom portion of the cup section 12 inthe axial direction and comprises a spline Sp serving as a torquetransmitting coupling portion formed at an outer periphery on an endportion thereof on an opposite side to the cup section 12. The outerjoint member 11 is formed by welding a cup member 12 a and a shaftmember 13 a to each other.

The cup member 12 a illustrated in FIG. 2a to FIG. 2c is anintegrally-formed product being made of medium carbon steel, such asS53C, containing carbon of from 0.40 wt % to 0.60 wt %, and having acylindrical portion 12 a 1 and a bottom portion 12 a 2. The cylindricalportion 12 a 1 has the track grooves 30 and the cylindrical innerperipheral surface 42 formed at an inner periphery thereof. A projectingportion 12 a 3 is formed at the bottom portion 12 a 2 of the cup member12 a. A boot mounting groove 32 is formed at an outer periphery of thecup member 12 a on the opening side thereof, whereas a snap ring groove33 is formed at an inner periphery of the cup member 12 a on the openingside thereof. A bearing mounting surface 14 and a snap ring groove 15are formed at an outer periphery of the shaft member 13 a on the cupmember 12 a side, whereas the spline Sp is formed at an end portion ofthe shaft member 13 a on an opposite side.

The shaft member 13 a is made of medium carbon steel, such as S40C,containing carbon of from 0.30 wt % to 0.55 wt %. A joining end surface50 formed at the projecting portion 12 a 3 of the bottom portion 12 a 2of the cup member 12 a and a joining end surface 51 formed at an endportion of the shaft member 13 a on the cup member 12 a side are broughtinto abutment against each other, and are welded to each other byelectron beam welding performed from an outer side of the cup member 12a in a radial direction. As illustrated in FIG. 2a and FIG. 2b , awelded portion 49 is formed of a bead, which is formed by a beamradiated from a radially outer side of the cup member 12 a. Althoughdetailed description is made later, outer diameters B1 and B2 of thejoining end surface 50 and the joining end surface 51 (see FIG. 4b andFIG. 5c ) are set to equal dimensions for each joint size. However, theouter diameter B1 of the joining end surface 50 of the cup member 12 aand the outer diameter B2 of the joining end surface 51 of the shaftmember 13 a need not be set to equal dimensions. In consideration of,for example, a state of the weld bead, a dimensional difference may begiven as appropriate in such a manner that the outer diameter B2 of thejoining end surface 51 is set slightly smaller than the outer diameterB1 of the joining end surface 50, or that the outer diameter B2 of thejoining end surface 51 is set slightly larger than the outer diameter B1of the joining end surface 50, conversely. The description “the outerdiameters B1 and B2 of the joining end surface 50 and the joining endsurface 51 are set to equal dimensions for each joint size” hereinrefers to a concept encompassing a case in which the dimensionaldifference is given as appropriate between the outer diameter B1 of thejoining end surface 50 and the outer diameter B2 of the joining endsurface 51.

As illustrated in FIG. 2a to FIG. 2c , the welded portion 49 is formedon the joining end surface 51 located on the cup member 12 a side withrespect to the bearing mounting surface 14 of the shaft member 13 a, andhence the bearing mounting surface 14 and the like can be processed inadvance so that post-processing after welding can be omitted. Further,the electron beam welding does not cause formation of burrs at thewelded portion. Thus, post-processing for the welded portion can also beomitted, thereby being capable of reducing manufacturing cost. Stillfurther, total inspection on the welded portion through ultrasonic flawdetection can be performed. As a feature, the manufacturing methodaccording to the first embodiment comprises an ultrasonic flawdetection-inspection step which enables defect detection for an entireregion of a welded portion, that is, a region of the welded portion froma surface to an inside of an outer joint member of a constant velocityuniversal joint being a mass-produced product with high detectionaccuracy and also at the level of enabling industrial production.Details thereof are described later.

As illustrated in FIG. 2c , the joining end surface 50 of the cup member12 a is formed by annular turning, and a center portion in a radialdirection maintains a forged surface. With this, a turning time isshortened. An annular groove portion 51 a is formed on a radially innerside of the joining end surface 51 of the shaft member 13 a, and anannular blocking portion 51 b is formed more on a radially inner side.The annular groove portion 51 a is formed in a weld joint interfacedirectly below a bead of the welded portion 49 (see FIG. 2b ). When theboth joining end surfaces 50 and 51 are brought into abutment againsteach other, a hollow cavity portion H is formed. The annular grooveportion 51 a and the hollow cavity portion H are separated and blockedby the annular blocking portion 51 b. The welded portion 49 having theannular groove portion 51 a and the annular blocking portion 51 b has acomplicated workpiece shape subjected to ultrasonic flaw detectioninspection described later.

When the cup member 12 a and the shaft member 13 a described above arebrought into abutment against each other, and electron beam welding isperformed in a vacuum (low pressure) atmosphere at the level of enablingindustrial production of a constant velocity universal joint being amass-produced product, no recess is formed on the radially inner side ofthe bead of the welded portion 49 as illustrated in FIG. 2b . Further,the radially inner end portion of the weld bead is sufficiently formedto reach the annular groove portion 51 a. It is considered that theinternal pressure of residual air in the hollow cavity portion H isblocked by the annular blocking portion 51 b, or a volume of theresidual air in the annular groove portion 51 a is small, and hence theamount of expansion in volume due to heating is small, therebysuppressing the influence of the internal pressure. With thisconfiguration, the strength, quality, and reliability of the weldedportion can be improved. The annular groove portion 51 a has a width offrom about 1 mm to about 3 mm and a depth of from about 0.6 mm to 2 mm.A flat smooth surface is formed by removing the outer surface includingthe welded portion 49 by turning as illustrated in FIG. 2a and FIG. 2 b.

Next, the manufacturing method according to the first embodiment of thepresent invention is described with reference to FIG. 3 to FIG. 24.Before description of details of the features of the manufacturingmethod according to the first embodiment, that is, an ultrasonic flawdetection-inspection step for the welded portion, an overview ofmanufacturing steps (processing steps) is described. FIG. 3 is anillustration of the overview of the manufacturing steps for the outerjoint member. In the first embodiment, as illustrated in FIG. 3, the cupmember 12 a is manufactured through manufacturing steps comprising a barmaterial cutting step S1 c, a forging step S2 c, and ironing step S3 c,and a turning step S4 c. Meanwhile, the shaft member 13 a ismanufactured through manufacturing steps comprising a bar materialcutting step S1 s, a turning step S2 s, and a spline processing step S3s. Intermediate components of the cup member 12 a and the shaft member13 a thus manufactured are each assigned with a product number formanagement.

After that, the cup member 12 a and the shaft member 13 a are subjectedto a welding step S6, a removal processing step S6 j, an ultrasonic flawdetection-inspection step S6 k, a heat treatment step S7, and a grindingstep S8 so that the outer joint member 11 is completed.

An overview of each step is described. Each step is described as atypical example, and appropriate modification and addition may be madeto each step as needed. First, the manufacturing steps for the cupmember 12 a are described.

[Bar Material Cutting Step S1 c]

A bar material is cut into a predetermined length in accordance with aforging weight, thereby producing a billet.

[Forging Step S2 c]

The billet is subjected to forging so as to integrally form thecylindrical portion, the bottom portion, and the projecting portion as apreform of the cup member 12 a.

[Ironing Step S3 c]

Ironing is performed on the track grooves 30 and the cylindrical innerperipheral surface 42 of the preform, thereby finishing the innerperiphery of the cylindrical portion of the cup member 12 a.

[Turning Step S4 c]

In the preform after ironing, the outer peripheral surface, the bootmounting groove 32, the snap ring groove 33, the joining end surface 50,and the like are formed by turning. In the first embodiment, after theturning step S4 c, the cup member 12 a in the form of an intermediatecomponent is assigned with a product number for management.

Next, the manufacturing steps for the shaft member 13 a are described.

[Bar Material Cutting Step S1 s]

A bar material is cut into a predetermined length in accordance with theentire length of the shaft section, thereby producing a billet. Afterthat, the billet is forged into a rough shape by upset forging dependingon the shape of the shaft member 13 a in some cases.

[Turning Step S2 s]

The outer peripheral surface of the billet or the preform (bearingmounting surface 14, snap ring groove 15, minor diameter of the spline,end surface, and the like), the joining end surface 51 of the billet atthe end portion on the cup member 12 a side, and the annular grooveportion 51 a are formed by turning.

[Spline Processing Step S3 s]

The spline is formed by rolling in the shaft member after turning. Notethat, the processing for the spline is not limited to the rolling, andpress working or the like may be adopted instead as appropriate. In thefirst embodiment, after the spline processing, the shaft member 13 a inthe form of an intermediate component is assigned with a product numberfor management.

Next, the manufacturing steps in the process of completing the outerjoint member 11 from the cup member 12 a and the shaft member 13 a aredescribed.

[Welding Step S6]

The joining end surface 50 of the cup member 12 a and the joining endsurface 51 of the shaft member 13 a are brought into abutment againsteach other and welded.

[Removal Processing Step S6 j]

A flat smooth surface 55 (see FIG. 2b ) is formed by removing the outersurface including the welded portion 49 of the cup member 12 a and theshaft member 13 a by turning.

[Ultrasonic Flaw Detection-Inspection Step S6 k]

The welded portion 49 between the cup member 12 a and the shaft member13 a is inspected by the ultrasonic flaw-detection method.

[Heat Treatment Step S7]

Induction quenching and tempering are performed as heat treatment on atleast the track grooves 30 and the cylindrical inner peripheral surface42 of the cup section 12 after welding and a necessary range of theouter periphery of the shaft section 13 after welding. Heat treatment,is not performed on the welded portion. A hardened layer having ahardness of approximately from 58 HRC to 62 HRC is formed on each of thetrack grooves 30 and the cylindrical inner peripheral surface 42 of thecup section 12. Further, a hardened layer having a hardness ofapproximately from 50 HRC to 62 HRC is formed in a predetermined rangeof the outer periphery of the shaft section 13.

[Grinding Step S8]

After the heat treatment, the bearing mounting surface 14 of the shaftsection 13 and the like are finished by grinding. Thus, the outer jointmember 11 is completed.

In the manufacturing steps of the first embodiment, the heat treatmentstep is provided after the welding step, and hence the manufacturingsteps are suited to a cup member and a shaft member having such shapesand specifications that the hardness of the heat-treated portion may beaffected by temperature rise at the periphery due to heat generatedduring the welding.

Next, main constituent features of the manufacturing method of the firstembodiment are described. FIG. 4a is a vertical sectional view forillustrating a state after ironing of the cup member 12 a. FIG. 4b is avertical sectional view for illustrating a state after turning. In apreform 12 a′ for the cup member 12 a, a cylindrical portion 12 a 1′, abottom portion 12 a 2′, and a projecting portion 12 a 3′ are integrallyformed in the forging step S2 c. After that, the track grooves 30 andthe cylindrical inner peripheral surface 42 are formed by ironing in theironing step S3 c so that the inner periphery of the cylindrical portion12 a 1′ is finished as illustrated in FIG. 4 a.

After that, in the turning step S4 c, the outer peripheral surface, theboot mounting groove 32, the snap ring groove 33, and the like of thecup member 12 a as well as the joining end surface 50 of the projectingportion 12 a 3 of the bottom portion 12 a 2, and the outer diameter B1portion thereof are formed by turning as illustrated in FIG. 4 b.

FIG. 5 are illustrations of states of the shaft member 13 a in therespective processing steps. FIG. 5a is a front view for illustrating abillet 13 a″ obtained by cutting a bar material. FIG. 5b is a partialvertical sectional view for illustrating a preform 13 a′ obtained byforging the billet 13 a″ into a rough shape by upset forging. FIG. 5c isa partial vertical sectional view for illustrating the shaft member 13 aafter turning and spline processing.

The billet 13 a″ illustrated in FIG. 5a is produced in the bar materialcutting step S1 s. The preform 13 a′ is produced by increasing the shaftdiameter of the billet 13 a″ in a predetermined range and forming arecessed portion 52 at a joining-side end portion (end portion on thecup member 12 a side) by upset forging as needed as illustrated in FIG.5 b.

After that, in the turning step S2 s, the outer diameter portion of theshaft member 13 a, the bearing mounting surface 14, the snap ring groove15, an inner diameter surface 53 (inner diameter E) of the recessedportion 52, the joining end surface 51, the outer diameter B2 portionthereof, and the annular groove portion 51 a are formed by turning asillustrated in FIG. 5c . In the spline processing step S3 s, the splineSp is processed at the end portion on the opposite side to the recessedportion 52 by rolling or press forming.

The outer diameter B1 of the joining end surface 50 of the cup member 12a illustrated in FIG. 4b is set to an equal dimension for one jointsize. Further, in the shaft member 13 a illustrated in FIG. 5c , whichis used as a long stem shaft, the outer diameter B2 of the joining endsurface 51 is set to an equal dimension for one joint size irrespectiveof the shaft diameter and the outer peripheral shape. Still further, thejoining end surface 51 of the shaft member 13 a is located at theposition on the cup member 12 a side with respect to the bearingmounting surface 14. Through the setting of dimensions as describedabove, the outer joint member 11 compatible with various vehicle typescan be manufactured in such a manner that, while the cup member 12 a isprepared for common use, only the shaft member 13 a is manufactured tohave a variety of shaft diameters, lengths, and outer peripheral shapesdepending on vehicle types, and both the members 12 a and 13 a arewelded to each other. Details of the preparation of the cup member 12 afor common use are described later.

Next, a method of welding the cup member 12 a and the shaft member 13 ais described with reference to FIG. 6 and FIG. 7. FIG. 6 and FIG. 7 areviews for illustrating an overview of a welding apparatus. FIG. 6 is anillustration of a state before welding. FIG. 7 is an illustration of astate during welding. As illustrated in FIG. 6, a welding apparatus 100mainly comprises an electron gun 101, a rotation device 102, a chuck103, a center hole guide 104, a tailstock 105, work-piece supports 106,a center hole guide 107, a case 108, and a vacuum pump 109.

The cup member 12 a and the shaft member 13 a being workplaces areplaced on the workplace supports 106 arranged inside the weldingapparatus 100. The chuck 103 and the center hole guide 107 arranged atone end of the welding apparatus 100 are coupled to the rotation device102. The chuck 103 grips the cup member 12 a under a state in which thecentering of the cup member 12 a is performed by the center hole guide107, thereby applying rotational movement. The center hole guide 104 isintegrally mounted to the tailstock 105 arranged at another end of thewelding apparatus 100. Both the center hole guide 104 and the tailstock105 are configured to reciprocate in the axial direction (right-and-leftdirection, in FIG. 6 and FIG. 7).

A center bole of the shaft member 13 a is set on the center hole guide104 so that the centering of the shaft member 13 a is performed. Thevacuum pump 109 is connected to the case 108 of the welding apparatus100. A “sealed space” herein refers to a space 111 defined by the case108. In the first embodiment, the cup member 12 a and the shaft member13 a are entirely received in the sealed space 111. The electron gun 101is arranged at a position corresponding to the joining end surfaces 50and 51 of the cup member 12 a and the shaft member 13 a. The electrongun 101 is configured to approach the workpieces up to a predeterminedposition.

Next, the operation of the welding apparatus 100 constructed asdescribed above and the welding method are described. The cup member 12a and the shaft member 13 a being workpieces are stocked at a placedifferent from the place of the welding apparatus 100. The respectiveworkpieces are taken out by, for example, a robot, are conveyed into thecase 108 of the welding apparatus 100 opened to the air as illustratedin FIG. 6, and are set at predetermined positions on the workpiecesupports 106. At this time, the center hole guide 104 and the tailstock105 retreat to the right side of FIG. 6, and hence a gap is formedbetween the joining end surfaces 50 and 51 of the cup member 12 a andthe shaft member 13 a. After that, a door (not shown) of the case 108 isclosed, and the vacuum pump 109 is activated to reduce the pressure inthe sealed space 111 defined in the case 108. Thus, the pressures in therecessed portion 52 and the inner diameter portion 53 of the shaftmember 13 a are reduced as well.

When the pressure in the sealed space 111 is reduced to a predeterminedpressure, the center hole guide 104 and the tailstock 105 are caused toadvance to the left side as illustrated in FIG. 7 to eliminate the gapbetween the joining end surfaces 50 and 51 of the cup member 12 a andthe shaft member 13 a. With this action, the hollow cavity portion Hwhich is reduced in pressure is formed between the joining end surface50 of the cup member 12 a and the inner diameter surface 53 and therecessed portion 52 of the shaft member 13 a, and the annular grooveportion 51 a which is reduced in pressure is formed while being blockedby the annular blocking portion 51 b [see FIG. 2c ] from the hollowcavity portion H. The centering of the cup member 12 a is performed bythe center hole guide 107, and is fixed by the chuck 103, whereas theshaft member 13 a is supported by the center hole guide 104. After that,the workpiece supports 106 are moved away from the workpieces. At thistime, the distance between the workpiece supports 106 and the workpiecesmay be infinitesimal, and hence illustration of this distance is omittedfrom FIG. 7. As a matter of course, the welding apparatus 100 may havesuch a structure that the workpiece supports 106 retreat downwardgreatly.

Although illustration is omitted, the electron gun 101 is then caused toapproach the workpieces up to a predetermined position, and theworkpieces are rotated to start pre-heating. As a pre-heating condition,unlike the welding condition, the temperature is set lower than thewelding temperature by, for example, radiating an electron beam under astate in which the electron gun 101 is caused to approach the workpiecesso as to increase the spot diameter. Through the pre-heating, thecooling rate after welding is reduced, thereby being capable ofpreventing a quenching crack. When a predetermined pre-heating time haselapsed, the electron gun 101 retreats to a predetermined position, andradiates the electron beam from the outer side of the workpieces in theradial direction to start welding. When the welding is terminated, theelectron gun 101 retreats, and rotation of the workpiece is stopped.

Although illustration is omitted, the sealed space 111 is then opened tothe air. Then, under a state in which the workpiece supports 106 areraised to support the workpieces, the center hole guide 104 and thetailstock 105 retreat to the right side, and the chuck 103 is opened.After that, for example, the robot grips the workpieces, takes theworkpieces out of the welding apparatus 100, and places the workpiecesinto alignment on a cooling stocker. In the first embodiment, the cupmember 12 a and the shaft member 13 a entirely received in the sealedspace 111, and hence the configuration of the sealed space 111 definedin the case 108 can be simplified.

Specifically, the cup member 12 a having a carbon content of from 0.4%to 0.6% and the shaft member 13 a having a carbon content of from 0.3%to 0.55% were used and welded to each other in the above-mentionedwelding apparatus 100 under the condition that the pressure in thesealed space 111 defined in the case 108 was set to 6.7 Pa or less. Inorder to prevent the cup member 12 a and the shaft member 13 a frombeing cooled rapidly after the welding to suppress increase in hardnessof the welded portion, the joining end surfaces 50 and 51 of the cupmember 12 a and the shaft member 13 a were soaked by pre-heating to havea temperature of from 300° C. to 650° C., and then electron beam weldingwas performed. As a result, a welded portion having no recess on aradially inner side of a weld bead was obtained. Further, through thesoaking by pre-heating, the hardness of the welded portion aftercompletion of the welding was able to be kept within a range of from 200Hv to 500 Hv, thereby being capable of attaining high welding strengthand stable welding state and quality. Still further, the cup member 12 aand the shaft member 13 a were welded to each other under the conditionthat the pressure in the sealed space 111 of the welding apparatus 100was set to an atmospheric pressure or less, thereby being capable ofsuppressing the change in pressure in the hollow cavity portion duringthe welding. As a result, the blowing of a molten material and the entryof the molten material toward the radially inner side were able to beprevented. Setting of the pressure in the sealed space 111 defined inthe case 108 to 6.7 Pa or less is a vacuum (low pressure) condition atthe level of enabling industrial production of the constant velocityuniversal joint being a mass-produced product for automobiles and thelike.

In the outer joint member 11 of the first embodiment, as illustrated inFIG. 2b , the annular groove portion 51 a is formed in a weld jointinterface directly below the bead of the welded portion 49 on theradially inner side of the joining end surface 51 of the shaft member 13a, and the annular blocking portion 51 b is formed more on a radiallyinner side. The annular groove portion 51 a and the hollow cavityportion H are separated and blocked by the annular blocking portion 51b.

It has been found that, when the cup member 12 a and the shaft member 13a having the configuration described above are brought into abutmentagainst each other, and electron beam welding is performed, asillustrated in FIG. 2b , no recess is formed on the radially inner sideof the bead of the welded portion 49, and the radially inner end portionof the weld bead is sufficiently formed to reach the annular grooveportion 51 a. It is considered that the internal pressure in the hollowcavity portion H is blocked by the annular blocking portion 51 b, or avolume of the residual air in the annular groove portion 51 a is small,and hence the amount of expansion in volume due to heating is small,thereby suppressing the influence of the internal pressure. With thisconfiguration, the strength, quality, and reliability of the weldedportion can be improved.

Following the above description of the overview of the manufacturingstep (processing steps) of the first embodiment, the features of thefirst embodiment, that is, the ultrasonic flaw detection-inspection stepfor the welded portion is described with reference to FIG. 8 to FIG. 19.FIG. 8a is a vertical sectional view for illustrating a state of thewelded portion after the welding step S6. FIG. 8b is a verticalsectional view for illustrating a state after the removal processingstep S6 j for the outer surface including the welded portion. FIG. 9 isa graph for showing detection results of a surface reflection echo withvarious surface roughness. FIG. 10 is a front view for illustrating anoverview of an ultrasonic flaw detection-inspection apparatus. FIG. 11is a plan view, and FIG. 12 is a right side view. In each of the statesillustrated in FIG. 10 to FIG. 12, the outer joint member after weldingis placed in the ultrasonic flaw detection-inspection apparatus. FIG. 13is a right side view for illustrating a state in which the centering ofthe outer joint member is performed by upper and lower center holeguides. FIG. 14 is a plan view for illustrating a state in which a probehas moved to a flaw detection position after the centering of FIG. 13.FIG. 15 is a partial plan view for illustrating a positionalrelationship between the probe and the outer joint member. FIG. 16 toFIG. 18 are views for illustrating an overview of states of ultrasonicflaw detection inspection. FIG. 19 to FIG. 21 are explanatory graphs forshowing an overview of a quality determination program for a detectionresult of a defect of the welded portion.

First, description is made of a knowledge obtained during thedevelopment process with regard to the dead zone of the welded portion49 caused by the surface reflection echo. The outer surface of the beadof the welded portion 49 after the welding step S8 has a fine unevenshape slightly protruding from radially outer surfaces of the cup member12 a and the shaft member 13 a as illustrated in FIG. 8a . Therefore. Ithas been found that, when the ultrasonic waves are irradiated to thesurface of the welded portion 49, formation of the dead zone caused bythe surface reflection echo is inevitable.

Therefore, focus was given to remove the outer surface including thewelded portion 49 to form a flat smooth surface before ultrasonic flawdetection inspection. As the removal processing for forming the flatsmooth surface, it is desired that grinding be performed in view of thesurface characteristics. However, there is difficulty in performing theremoval processing for the welded portion of the outer joint member ofthe constant velocity universal joint being a mass-produced product forautomobiles and the like at the level of enabling industrial production.Accordingly it has been concluded that removal processing by turning isessential.

Then, experiments were conducted with different incident directions ofthe ultrasonic waves to the flat smooth surface having been subjected toremoval by turning and having turning marks extending in acircumferential direction. As a result of the experiments, it was foundthat the dead zone caused by the surface reflection echo was formed whenthe ultrasonic waves were irradiated in a direction perpendicular to theturning marks, whereas the dead zone caused by the surface reflectionecho was not formed when the ultrasonic waves were irradiated in adirection parallel to the turning marks. It is considered that thesurface reflection echo is liable to be affected by irregular reflectionof the ultrasonic waves when the ultrasonic waves are irradiated in thedirection perpendicular to the turning marks, whereas the surfacereflection echo is less liable to be affected by the irregularreflection when the ultrasonic waves are irradiated in the directionparallel to the turning marks.

Further, it was found that, even when the surface reflection echo wasless liable to be affected by the irregular reflection of the ultrasonicwaves with the irradiation of the ultrasonic waves in the directionparallel to the turning marks, the surface reflection was affected bythe surface roughness, and larger surface, roughness caused highersurface reflection echo as a whole, with the result that the echo wasnot able to be distinguished from the echo from the defect. Detectionresults of peak values of the surface reflection echo with varioussurface roughness are shown in FIG. 9. In FIG. 9, the horizontal axisrepresents a surface roughness, and the vertical axis represents a peakvalue of the reflection echo. Based on the detection results, when thesurface roughness Ra is smaller, the surface reflection echo becomessmaller. The echo of a product having good quality (base echo) is 10% orless. Therefore, it is considered that the surface roughness Ra whichdoes not affect the measurement is desirably 2.0 μm or less.

Based on the knowledge described above, the following conditions weredetermined, and hence the configuration with regard to the flat smoothsurface and the irradiation method in the first embodiment wereachieved.

(1) The flat smooth surface having been subjected to removal by turningand having turning marks extending in the circumferential direction isobtained.

(2) The circumferential angle beam flaw detection method of irradiatingthe ultrasonic waves in the direction parallel to the turning marks isemployed.

(3) The surface roughness Ra of the flat smooth surface is set to 2.0 μmor less.

FIG. 8b is an illustration of the flat smooth surface 55 which isobtained by removing the outer surface including the welded portion 49by turning in the removal processing step S6 j illustrated in FIG. 3. Inthe first embodiment, the surface roughness Ra of the flat smoothsurface 55 is set to 0.8 μm. The flat smooth surface 55 has turningmarks extending in the circumferential direction. Details of thecircumferential angle beam flaw detection method of irradiating theultrasonic waves in the direction parallel to the turning marks aredescribed later.

Next, the ultrasonic flaw detection-inspection apparatus is describedwith reference to FIG. 10 to FIG. 18. As illustrated in FIG. 10 to FIG.12, an ultrasonic flaw detection-inspection apparatus 120 mainlycomprises a water bath 122 mounted to a base 121, a workpiece support123, a lifting device 147 for the workpiece support 123, an upper centerhole guide 124, a drive positioning device 128 for the upper center holeguide 124, a lower center hole guide 126, a rotary drive device 125configured to rotate an intermediate product 11′ (hereinafter alsoreferred to as “workpiece 11”) of the outer joint member 11, and a drivepositioning device 161 for the probe 160. An outer frame of theultrasonic flaw detection-inspection apparatus 120 is an assembly of aframe 133, and the base 121 is mounted to the frame 133.

As illustrated in FIG. 12, the drive positioning device 128 for theupper center hole guide 124 comprises a vertical-direction drivepositioning device 129 and a horizontal-direction drive positioningdevice 130. The horizontal-direction drive positioning device 130 isprovided to an upper end portion of a support column 132 feed to thebase 121. The horizontal-direction drive positioning device 130 mainlycomprises linear-motion bearings 135, a moving member 136, and a drivecylinder 137. The linear-motion bearings 135 are mounted to the upperend portion of the support column 132, and comprise rails 134 and linearguides 135 a. The drive cylinder 137 is coupled to the moving member136. The moving member 136 is driven and positioned in the horizontaldirection by the drive cylinder 137.

The vertical-direction drive positioning device 129 is provided to asupport member 138 mounted to the moving member 136 of thehorizontal-direction drive positioning device 130. Thevertical-direction drive positioning device 129 mainly comprises theupper center hole guide 124, a drive cylinder 142, and a linear-motionbearing 140. The drive cylinder 142 is coupled to the upper center holeguide 124. The linear-motion bearing 140 comprises a rail 139 and linearguides 141 mounted to the support member 138. The upper center holeguide 124 is driven and positioned in the vertical direction by thedrive cylinder 142. A center 124 a is rotatably mounted to the uppercenter hole guide 124 through intermediation of a rolling bearing or thelike (not shown). A set position of the drive cylinder 142 in thevertical direction is adjustable by a suitable mechanism such as afeed-screw mechanism (not shown) in accordance with a product number andan axial dimension of the workpiece 11′.

The lower center hole guide 126 is mounted to a rotary shaft 140 a of arotary support member 143 mounted to the base 121. The rotary shaft 143a is driven to rotate by a servomotor 145 mounted to a side plate 144.The rotary shaft 143 a has an engagement piece 146 which is engaged withthe track grooves 30 (see FIG. 2a ) of the workpiece 11′ to transmit arotational drive force. A center 126 a of the lower center hole guide126 is rotatable, but a position in the vertical direction is fixed.

The workpiece support 123 is mounted to the lifting device 147. Thelifting device 147 comprises a linear-motion bearing 149, a movingmember 151, and a drive cylinder 152. The linear-motion bearing 149comprises a rail 148 and linear guides 150 mounted to a side surface ofthe support column 132. The drive cylinder 152 is coupled to the movingmember 151. The workpiece support 123 is slightly movable in thevertical direction by the lifting device 147.

The drive positioning device 161 for the probe 100 is described withreference to FIG. 10 and FIG. 11. As illustrated in FIG. 10, a fixedmember 155 is provided to the base 121, and a drive cylinder (electriccylinder) 156 is mounted between the fixed member 155 and an upperportion of the frame 133. The fixed member 155 comprises a plate-shapedmember 155 a, and a rail 157 indicated by the two-dot chain lines ismounted to a back surface of the plate-shaped member 155 a. Abase member159 of the drive positioning device 161 for the probe 160 is arrangedopposed to the plate-shaped member 155 a. A linear guide 158 is mountedto the base member 159 so that the base member 159 is movable along therail 157. The base member 159 is coupled to the drive cylinder 156. Withthis configuration, the base member 159 is driven and positioned in thevertical direction, that is, in the Z-axis direction.

Rails 162 are mounted on the upper surface of the base member 159 in theright-and-left direction in FIG. 10, and a movable base 164 is providedthrough intermediation of linear guides 163. The movable base 164 iscoupled 10 to the drive cylinder (electric cylinder) 165 mounted to theupper surface of the base member 159. With this configuration, themovable base 164 is driven and positioned in the right-and-leftdirection in FIG. 10, that is, in the X-axis direction.

The movable base 164 comprises a mounting portion 164 a on an upperside, and a drive cylinder (electric cylinder) 166 is mounted to themounting portion 164 a. An arm member 167 of the probe 160 is mounted tothe drive cylinder 166. With this configuration, the arm member 167 isdriven and positioned in the front-and-rear direction of FIG. 10, thatis, in the Y-axis direction illustrated in FIG. 11.

As described above, the drive cylinders in the X-axis direction, theY-axis direction, and the Z-axis direction are electric cylinders of anelectric ball-screw type. Therefore, positioning with high accuracy canbe performed.

In the illustrations in FIG. 10, FIG. 12, and FIG. 13, for easyunderstanding of a state of arrangement of the members, a side wall ofthe water bath 122 on the near side in FIG. 10, FIG. 12, and FIG. 13 iscut, and a water surface is omitted. In the ultrasonic flawdetection-inspection apparatus 120 of the first embodiment, a flawportion of the workpiece 11′, the workpiece support 123, a part of themoving member 151, the lower center hole guide 126, a part of the rotarysupport member 143, and parts of the probe 160 and the arm member 167are arranged in the water bath 122 so as to be soaked in water.

Detailed description is made of the arm member 167 of the probe 160 withreference to FIG. 15. The probe 160 is mounted to a lower portion of thearm member 167. The probe 160 is mounted to a gear 168 throughintermediation of a holder 172. An electric rotary actuator 169 ismounted to an upper portion of the arm member 167, and a gear 170 havingthe same number of teeth and modules as those of the gear 168 is mountedto the electric rotary actuator 169. A rack 171 is in mesh with the gear168 and the gear 170. Therefore, a rotary motion of the electric rotaryactuator 169 is transmitted from the gear 170 to the rack 171 and thegear 168, and a rotation angle of the electric rotary actuator 169 and arotation angle of the probe 160 are equal to each other. With thisconfiguration, an incident angle of the probe 160 can be set variable.Backlash of the rack 171 and the gears 168 and 170 is suppressed, andhence the electric rotary actuate 169 and the probe 160 rotate insynchronization with each other. An original point of the rotation angleof the electric rotary actuator 169 is determined in the followingmanner. A bottom side of the holder 172 for the probe 160 is broughtinto abutment against an angle checking jig (not shown) to be in ahorizontal state, and a rotation angle of the electric rotary actuator169 in this state is set to the original point. The rotation angle ofthe electric rotary actuator 169 with respect to the original point isrepresented by R. In the first embodiment, the transmission mechanismusing the rack 171 and the gears 168 and 170 is exemplified. However,the transmission mechanism is not limited thereto. A transmissionmechanism using, for example, a timing belt and pulleys may also beused. In the first embodiment, the circumferential angle beam flawdetection method described later is employed. Therefore, the probe 160is set in a horizontal state. That is, a rotation angle R of theelectric rotary actuator 169 is set to 0°.

Next, description is made of an operation of the ultrasonic flawdetection-inspection apparatus 120 and an ultrasonic flawdetection-inspection step S6 k. First, with reference to FIG. 10 to FIG.12, description is made of a state before the workpiece 11′ afterwelding is placed. Water is supplied to the water bath 122. Asillustrated in FIG. 12, the upper center hole guide 124 waits at aposition retreated in the horizontal direction by the drive cylinder 107of the horizontal-direction drive positioning device 130. At this time,the upper center hole guide 124 is at a position retreated upward by anappropriate distance by the drive cylinder 142 of the vertical-directiondrive positioning device 129 so as to prevent interference with a shaftend of the workpiece 11′. The workpiece support 123 is positioned on anupper side by an appropriate distance by the drive cylinder 152 of thelifting device 147 so that the center 126 a of the lower center holeguide 126 is positioned on the near side of a position at which thecenter 126 a faces a center hole of the workpiece 11′.

As illustrated in FIG. 10 and FIG. 11, the arm member 167 of the probe160 waits at a position on the left-far side of the water bath 122 (seeFIG. 11) by controlling the positions of the Z-axis-direction drivecylinder 156, the Y-axis-direction drive cylinder 166, and theX-axis-direction drive cylinder 165 of the drive positioning device 161for the probe 160. This position is set as an original position andserves as an original point for a program described later. Positions inthe X-axis direction, the Y-axis direction, and the Z-axis direction arecontrolled by the program.

In the above-mentioned initial state, the workpiece 11′ after welding isplaced on the workpiece support 123 by a loader (not shown). FIG. 10 toFIG. 12 are each an illustration of a state before the workpiece 11′ isplaced on the workpiece support 123. Under the state in which theworkpiece 11′ is placed on the workpiece support 123, the center 126 aof the lower center hole guide 126 is at a position on the near side ofthe position at which the center 126 faces the center hole of theworkpiece 11′.

After that, as illustrated in FIG. 13, the upper center hole guide 124is caused to advance by the drive cylinder 137 of thehorizontal-direction, drive positioning device 130, and is positioned ata position in the horizontal direction of the upper center hole of theworkpiece 11′. Subsequently, the upper center bole guide 124 is causedto advance to a lower side by the drive cylinder 142 of thevertical-direction drive positioning device 129, and is fitted to theupper center hole of the workpiece 11′. Subsequently, as the uppercenter hole guide 124 is caused to advance, the workpiece support 123 islifted down. As a result, the center 126 a of the lower center holeguide 126 is fitted to the lower center bole of the workpiece 11′, andthe centering of the workpiece 11′ is performed.

After that, the Z-axis-direction drive cylinder 156 of the drivepositioning device 161 for the probe 150 causes the probe 160 to advancein the Z-axis direction (vertical direction) to a position correspondingto a flaw detection position. Further, the Y-axis-direction drivecylinder 166 causes the probe 160 to advance in the Y-axis direction(horizontal direction) to a position corresponding to the flaw detectionposition. Finally, the X-axis-direction drive cylinder 165 causes theprobe 160 to advance in the X-axis direction (horizontal direction). Asa result, as illustrated in FIG. 14 and FIG. 15, the probe 160 ispositioned at the flaw detection position. In the first embodiment,description is made of the example in which the probe 160 is driven andpositioned in the order of the Z-axis direction, the Y-axis direction,and the X-axis direction. However, the order is not limited to theabove-mentioned order, and may be suitably changed.

After the probe 160 is positioned at the flaw detection position, theultrasonic flaw detection inspection is performed. The defects of thewelded portion 49 may be present on the radially inner side, at thecenter, and on the radially outer side (surface) of the welded portion49 in the thickness. However, according to the ultrasonic flaw detectioninspection in the first embodiment, the ultrasonic waves are irradiatedto the flat smooth surface 55, which has been subjected to removalprocessing on the outer surface including the welded portion 49, withone probe 160 at an incident angle which prevents total reflection ofthe ultrasonic waves in the circumferential angle beam flaw detectionmethod, and the focal point of the ultrasonic waves of the probe 160 isset to a plurality of positions from the surface of the welded portion49 to the inside, to thereby perform inspection on the entire region ofthe welded portion 49. Specifically the ultrasonic waves are irradiatedto the flat smooth surface 55 having been subjected to removal byturning and having turning marks extending in the circumferentialdirection in the direction parallel to the turning marks. With thisconfiguration, it is possible to perform defect detection for an entireregion of the welded portion 49, that is, a region of the welded portion49 from the surface to the inside, of the outer joint member 11 of theconstant velocity universal joint 10 being a mass-produced product forautomobiles and the like with high detection accuracy and also at thelevel of enabling industrial production.

An overview of a specific inspection in the first embodiment isdescribed. Scanning positions of the probe 160 and target positions ofthe focal point of the ultrasonic waves are described with reference toFIG. 16 and FIG. 17. FIG. 16a to FIG. 16c are illustrations of a statein which the probe 160 scans in the axial direction (Z-axis direction).FIG. 16a is an illustration of a state in which the scanning position ofthe probe 160 is set to the shaft member 13 a side of the welded portion49. The probe 160 is moved from this state to the lower side in theZ-axis direction, to thereby set the scanning position of the probe 160at the center of the welded portion 49 in the axial direction asillustrated in FIG. 16b . Further, the probe 160 is moved to the lowerside in the Z-axis direction, to thereby set the scanning position ofthe probe 160 on the cup member 12 a side of the welded portion 49 asillustrated in FIG. 16c . With this action, the detect inspection on theentire region of the welded portion 49 in the axial direction can beperformed by one probe 160.

Next, the target positions of the focal point of the ultrasonic waves ofthe probe 160 are described with reference to FIG. 17a to FIG. 17c .FIG. 17a to FIG. 17c are illustrations of scanning positions of theprobe 160 using positions of the welded portion 49 at the center in theaxial direction as representative examples, and are partialcross-sectional views taken along the line I2-I2 of FIG. 16b . Thetarget positions of the focal point of the ultrasonic waves are also thesame for the case in which the scanning position of the probe 160 is onthe shaft member 13 a side of the welded portion (cross section takenalong the line I1-I1 of FIG. 16a ) and the case in which the scanningposition of the probe 160 is on the cup member 12 a side of the weldedportion 49 (cross section taken along the line I3-I3 of FIG. 16c ), andhence illustration thereof is omitted. The ultrasonic waves have a widthabout the axis G as illustrated in FIG. 17a to FIG. 17c , and form afocal point. The ultrasonic waves have high intensity at this focalpoint, and the detection accuracy for the defect becomes higher.

FIG. 17a is an illustration of a state in which the target position ofthe focal point of the ultrasonic waves is set to the radially innerside of the welded portion 49. In this case, a defect K1 which ispresent on the radially inner side of the welded portion 49 can bedetected. Next, when the probe 160 is moved in the X-axis direction(left side in the drawings) to set the target position of the focalpoint of the ultrasonic waves to the center of the welded portion 49 inthe thickness, as illustrated in FIG. 17b , a defect K2 which is presentat the center the welded portion 49 in the thickness of can be detected.When the probe 160 is further moved in the X-axis direction (left sidein the drawings) to set the target position of the focal point of theultrasonic waves on the radially outer side (surface) of the weldedportion 49, as illustrated in FIG. 17c , a defect K3 which is present onthe radially outer side of the welded portion 49 can be detected. Withthis action, defect inspection for an entire region of the weldedportion 49, that is, a region of the welded portion 49 from the surfaceto the inside can be performed with the one probe 160.

An actual state of the ultrasonic flaw detection inspection isdescribed. For every inspection for the workpiece 11′, as describedabove, the probe 160 waits at the original position as illustrated inFIG. 10 and FIG. 11. After the workpiece 11′ is centered by theultrasonic flaw detection inspection apparatus 120, in accordance withan instruction by the program, the probe 160 proceeds to the flawdetection position illustrated in FIG. 14 and FIG. 15 and is positionedthereat. The flaw detection position is illustrated in FIG. 16a and FIG.17a . The scanning position of the probe 160 in the X-axis direction isset to the shaft member 13 a side of the welded portion 49 asillustrated in FIG. 16a , and the target position of the focal point(illustrated with a small ellipse or a small circle) of the ultrasonicwaves of the probe 160 is set to the radially inner side of the weldedportion 49 as illustrated in FIG. 17a . For simplification of thedrawings, hatching on the welded portion 49 is omitted. The same appliesto FIG. 17 and FIG. 18 to be referred to later.

In the circumferential angle beam flaw detection method, an axis of anultrasonic transmission pulse (hereinafter simply referred to“transmission pulse”) G of the probe 160 is perpendicular to an axis ofthe workpiece 11′ and is parallel to the vertical cross section of FIG.16a . At this time, the rotation angle R of the electric rotary actuator169 which changes the axis of the transmission pulse G of the probe 160is 0° (see FIG. 15). However, in a case of a probe of a type with aninclined axis of the transmission pulse, the rotation angle R of theelectric rotary actuator is adjusted by the degree of inclination tocause the axis of the transmission pulse G to be perpendicular to theaxis of the workpiece 11′ and be parallel to the vertical cross sectionof FIG. 16a . As illustrated in FIG. 17a , the probe 160 is positionedby being offset in the Y-axis direction. Therefore, an incident anglecorresponding to a circumferential inclination angle RC is formed, and arefraction angle RC′ is given.

As illustrated in FIG. 16a and FIG. 17a , with respect to the flatsmooth surface 55 having been subjected to removal by turning and havingturning marks extending in the circumferential direction, a transmissionpulse G is irradiated in the direction parallel to the turning marks.The incident direction, the incident angle RC, and the refraction angleRC′ of the transmission pulse G are the same in FIG. 16b , FIG. 16c ,FIG. 17b , and FIG. 17c to be referred to later. The incident angle RCis set to 18° which enables suppression of formation of the dead zone inthe vicinity of the surface and enables irradiation of the ultrasonicwaves also to the inside. The incident angle RC is set to the incidentangle which does not cause total reflection of the ultrasonic waves, andit is desired that the incident angle RC be set within the range of from10° to 27°.

The transmission pulse G is successively transmitted from the probe 160.The servomotor 145 (see FIG. 13) reversely rotates to a suitablerotation angle, and thereafter forwardly rotates to receive by one stepa reflection echo Gr1 for one rotation (360°) being associated with aphase angle as a first step with a phase angle of 0° as an originalpoint in a constant velocity rotation state. The defects K1, K2, and K3of the welded portion 40 may be present on the radially inner side, atthe center, and on the radially outer side (surface) of the thickness.However, in association with FIG. 17a , the defect K1 on the radiallyinner side of the thickness on the shaft member 13 a side of the weldedportion 49 is detected.

Next, as a second step, a position in the Z-axis direction, is shifted(positions in the X-axis direction and the Y-axis direction are notchanged, and the same applies to the next third step), and asillustrated in FIG. 16b , the probe 160 is positioned at the center ofthe welded portion 49 in the axial direction. Similarly to the firststep, the servomotor 145 rotates with the phase angle 0° as an originalpoint, and receives the reflection echo Gr1 for one rotation (360°)being associated with the phase angle. As a third step, the position inthe Z-axis direction is further shifted, and as illustrated in FIG. 16c, the probe 160 is positioned, on the cup member 12 a side of the weldedportion 49. Similarly to the previous step, the servomotor 145 receivesthe reflection echo Gr1 for one rotation (360°) being associated withthe phase angle. With this action, the defect inspection on the entireregion of the welded portion 49 in the axial direction is performed onthe defect K1 on the radially inner side of the welded portion 49 in thethickness.

Next, as a fourth step, the probe 160 is moved in the X-axis directionas illustrated in FIG. 17b to set the target position of the focal pointof the ultrasonic waves at the center of the welded portion 49 in thethickness, and the probe 160 is moved in the Z-axis direction to bepositioned at the position on the shaft member 13 a side of the weldedportion 49 (see FIG. 16a ). Similarly to the first to third steps, theservomotor 145 rotates with the phase angle 0° as an original point, andreceives a reflection echo Gr2 for one rotation (360°) being associatedwith the phase angle. Similarly, as a fifth step, the probe 160 is movedin the Z-axis direction for inspection at the center of the weldedportion 49 in the axial direction (see FIG. 16b ), and as a sixth step,the cup member 12 a side of the welded portion 49 is inspected. Withthis action, the defect inspection on the entire region of the weldedportion 49 in the axial direction is performed on the defect K2 at thecenter of the welded portion 49 in the thickness.

Next, as a seventh step, the probe 160 is further moved in the X-axisdirection as illustrated in FIG. 17c to set the target position of thefocal point of the ultrasonic waves at the radially outer side of thewelded portion 49, and the probe 160 is moved in the Z-axis direction tobe positioned at the position on the shaft member 13 a side of thewelded portion 49 (see FIG. 16a ) for inspection. Further, as an eighthstep, the probe 160 is moved hi the Z-axis direction for inspection atthe center of the welded portion 49 in the axial direction (see FIG. 16b), and as a ninth step, the cup member 12 a side of the welded portion49 is inspected. Similarly to the previous step, the servomotor 145rotates with the phase angle 0° as an original point, and receives areflection echo Gr3 for one rotation (360°) being associated with thephase angle. With this action, the defect inspection on the entireregion of the welded portion 49 in the axial direction is performed onthe defect K3 on the cup member 12 a side of the welded portion 49.

Through the defect inspection of the first to ninth steps describedabove, the defect inspection on the entire region of the welded portion49 can be performed with one probe 160. The range of the defectinspection for each step is illustrated in FIG. 18. The ranges of thedefect inspections in the first to ninth steps are indicated by thereference symbols S1 to S9, respectively. As illustrated in FIG. 18, theentire region of the welded portion 19 is covered by the ranges S1 to S9of the defect inspection, thereby being capable of performing the defectdetection for the entire region of the welded portion 49, that is, theregion of the welded portion 49 from the surface to the inside with highdetection accuracy and also at the level of enabling industrialproduction.

An example of command values of the program for each of the flawdetection methods described above is collectively shown in Table 1. Suchflaw detection program is set in advance for each product number. Anoperator can select a flaw detection program set for each product numberso that the inspection can automatically be performed after theworkpiece 11′ is provided. Thus, the control of positions and angles ofthe probe 160 based on command values of the program enables theinspection to be applied to complicated shapes of workpieces (outerjoint members) and to outer joint members having different productnumbers. At the same time, adjustment of setup for equipment can easilybe performed, thereby being capable of securing repeatability ofinspection.

TABLE 1 Position Position Position Rotation in X-axis in Y-axis inZ-axis Angle R of Step Direction Direction Direction Robot RotaryRemarks 1 3.0 5.0 2.0 0° Circumfer- 2 3.0 5.0 2.5 ential Angle 3 3.0 5.03.0 Beam Flaw 4 3.5 5.0 2.0 Detection 5 3.5 5.0 2.5 Method 6 3.5 5.0 3.0Incident 7 4.5 5.0 2.0 Angle 18° 8 4.5 5.0 2.5 9 4.5 5.0 3.0

The example of the steps and command values of the program for each ofthe flaw defection methods described above is not limited to the exampleshown in Table 1. In the example shown in Table 1, the scanning positionfor the welded portion 49 in the axial direction and the target positionof the focal point of the ultrasonic waves are each divided into threesections. However, the number of sections may suitably be increased ordecreased. Further, the order of the steps and command values maysuitably be corrected.

Next, with reference to FIG. 19 to FIG. 21, description is made of anoverview of an example of a quality determination program for adetection result of a defect of the welded portion. In the graph shownin FIG. 19, a reflection echo being a base without a defect (hereinafterreferred to as “base echo”) is shown. The threshold value X1 is set to atwofold value of a maximum value of the base echo (20%) as a reference,and the threshold value X2 is set to a threefold value of the maximumvalue of the base echo.

The reflection echo provides one data piece per 1°, and hence threehundred and sixty data pieces are provided for one rotation. Thethreshold value X1 was set for determination of quality in a case inwhich a small defect is detected. When ten or more data pieces of thereflection echo exceeding the threshold value X1 are detected in onerotation (360°) of the welded portion, it is determined that a producthas a poor quality. In the data of the reflection, echo shown in FIG.20, two data pieces exceed the threshold value X1 in one rotation of thewelded portion, and hence it is determined that a product has a goodquality.

The threshold value X2 was set for determination of a quality in a casein which a large defect is detected. When at least one data piece of thereflection echo exceeding the threshold value X2 is detected, for onerotation (360°) of the welded portion, it is determined that a producthas a poor quality. In the data of the reflection echo shown in FIG. 21,two data pieces exceed the threshold value X1, and hence it isdetermined that the product has a good quality in terms of the thresholdvalue X1. However, one data piece exceeds the threshold value X2, andhence it is eventually determined that the product has a poor quality.

As described above, when determination of poor quality is given based onany one of the threshold values X1 and X2, the workpiece 11′ isdetermined as having a poor quality. The inspection can automatically beperformed by performing the quality determination based on the data ofthe reflection echo with the threshold values X1 and X2. However,determination criteria for the quality determination may be suitablyadjusted in accordance with an actual state of the workpiece 11′.

After the flaw detection inspection is terminated, as illustrated inFIG. 10 to FIG. 12, the probe 160 returns to a waiting position, and theupper center hole guide 124 and the lower center hole guide 126 areseparated from the workpiece 11′. The workpiece 11′ is conveyed by theloader (not shown) from the ultrasonic flaw detection inspectionapparatus 120. In such a manner, the inspection for the workpiece 11′ issequentially repeated.

As described above, the ultrasonic flaw detection-inspection apparatus120 of the first embodiment mainly comprises the water bath 122 mountedto the base 121, the workpiece support 123, the lifting device 147 forthe workpiece support 123, the upper renter hole guide 124, the drivepositioning device 128 for the upper center hole guide 124, the lowercenter hole guide 126, the rotary drive device 125 configured to rotatethe intermediate product 11′ (hereinafter also referred to as “workpiece11”) of the outer joint member 11, and the drive positioning device 161for the probe 160. With this configuration, the operations of supply ofwater, drainage of water, conveyance of the workpiece 11′ to theultrasonic flaw detection inspection apparatus 120, flaw detectioninspection, and conveyance of the workpiece 11′ from the ultrasonic flawdetection inspection apparatus 120 can be performed in conjunction,thereby being capable of automating the ultrasonic flaw detectioninspection. Thus, through irradiation of the ultrasonic waves to theflat smooth surface 55 having been subjected to the removal processingof the outer surface including the welded portion 49 by the one probe160 at the incident angle which does not cause total reflection of theultrasonic waves in the circumferential angle beam flaw detectionmethod, and setting of the focal point of the ultrasonic waves of theprobe 160 to the plurality of positions from the surface to the insideof the welded portion 49 to perform inspection on the entire region ofthe welded portion 49, it is possible to perform the defect detectionfor the entire region of the welded portion 49, that is, the region ofthe welded portion 49 from the surface to the inside of the outer jointmember 11 of the constant velocity universal joint 10 being amass-produced product for automobiles and the like with the highdetection accuracy and also at the level of enabling industrialproduction, and in addition, the accuracy, the operability, and theefficiency in the inspection can be enhanced. Thus, the ultrasonic flawdetection inspection apparatus 120 is suitable for inspection on awelded portion of an outer joint member of a constant velocity universaljoint being a mass-produced product.

Further, the outer diameter B1 of the joining end surface 50 of the cupmember 12 a of the first embodiment is set to an equal dimension foreach joint size. Also with this base configuration, in the ultrasonicflaw detection inspection, setup operations with respect to the outerjoint members 11 having the different product numbers are simplified.Thus, the efficiency in the inspection can be further enhanced. Stillfurther, flaw detection is performed under water, and hence ultrasonicwaves are satisfactorily propagated. Thus, inspection can be performedwith higher accuracy.

Next, to summarize the manufacturing concept, standardization of aproduct type of the cup member is additionally described whileexemplifying a shaft member having a product number different from thatof the above-mentioned shaft member 13 a of the long stem typeillustrated in FIG. 5. A shaft member 13 b illustrated in FIG. 22 andFIG. 23 is used as a general stem type on the inboard side. The shaftmember 13 b has the joining end surface 51 to be brought into abutmentagainst the joining end surface 50 [see FIG. 4b ] of the bottom portion12 a 2 (projecting portion 12 a 3) of the cup member 12 a. The outerdiameter B2 and the inner diameter E of the joining end surface 51 areset to the equal dimensions to the outer diameter B2 and the innerdiameter E of the joining end surface 51 of the shaft member 13 a of thelong stem type illustrated in FIG. 5 c.

The shaft member 13 b is used as the general stem type on the inboardside. Accordingly, the shaft member 13 b comprises a shaft section witha small length, and a sliding bearing surface 18 formed on an axialcenter portion thereof, and a plurality of oil grooves 19 are formed inthe sliding bearing surface 18. The spline Sp and a snap ring groove 48are formed in an end portion of the shaft member 13 b on the sideopposite to the cup member 12 a side. As described above, even whenthere are differences in types, such as the general length stem type andthe long stem type, and shaft diameters and outer peripheral shapes varyin each vehicle type, the outer diameter B2 of the joining end surface51 of the shaft members 13 a and 13 b is set to an equal dimension.

The outer diameters B (B1 and B2) of the joining end surface 50 of thecup member 12 a and the joining end surface 51 of the shaft members 13 aand 13 b are set to an equal dimension for each joint size. Thus, thecup member prepared for common use for each joint size, and the shaftmember having a variety of specifications of the shaft section for eachvehicle type can be prepared in a state before heat treatment. Further,the intermediate component of each of the cup member 12 a and the shaftmembers 13 a and 13 b can be assigned with a product number formanagement. Even when standardizing product types of the cup member 12a, various types of the outer joint members 11 satisfying requirementscan be produced quickly through combination of the cup member 12 a andthe shaft members 13 a and 13 b each having a variety of specificationsof the shaft section for each vehicle type. Therefore, standardizationof a product type of the cup member 12 a can reduce cost and alleviate aburden of production management.

The standardization of the product type of the cup member is describedabove by taking the differences in types, such as the general lengthstem type and the long stem type, as an example for easy understanding,but the present invention is not limited thereto. The same applies tostandardization of the product type of the cup member for shaft membershaving a variety of specifications of the shaft section for each vehicletype among the general length stem types, and for shaft members having avariety of specifications of the shaft section for each vehicle typeamong the long stem types.

As a summary of the above description, FIG. 24 is a diagram forillustrating an example of standardization of a product type of the cupmember according to the first embodiment. As illustrated in FIG. 24, thecup member is prepared for common use for one joint size, and isassigned with, for example, a product number C001 for management. Incontrast, the shaft member has a variety of specifications of the shaftsection for each vehicle type, and is assigned with, for example, aproduct number S001, S002, or S(n) for management. For example, when thecup member assigned with the product number C001 and the shaft memberassigned with the product number S001 are combined and welded to eachother, the outer joint member assigned with a product number A001 can beproduced. Thus, owing to standardization of a product type of the cupmember, it is possible to reduce cost and to alleviate a burden ofproduction management. In the standardization of a product type, the cupmember is not limited to one type for one joint size, that is, notlimited to one type assigned with a single product number. For example,the cup member comprises cup members of a plurality of types (assignedwith a plurality of product numbers, respectively) that are prepared forone joint size based on different specifications of a maximum operatingangle, and are each prepared so that the outer diameter B1 of thejoining end surface of each of those cup members has an equal dimension.

Next, with reference to FIG. 25 and FIG. 26, description is made of aconstant velocity universal joint and an outer joint member which are oftypes different from those of the constant velocity universal joint, andthe outer joint member of FIG. 1 and FIG. 2a which are manufacturedbased on the manufacturing method according to the first embodiment ofthe present invention. With regard to the constant velocity universaljoint and the outer joint member, the parts having the same functions asthose of the constant velocity universal joint and the outer jointmember illustrated in FIG. 1 and FIG. 2a are denoted by the samereference symbols (except for subscripts), and only the main points aredescribed.

A plunging type constant velocity universal joint 10 ₂ illustrated inFIG. 25 is a tripod type constant velocity universal joint (TJ), andcomprises an outer joint member 11 ₂ comprising a cup section 12 ₂ andthe long stem section 13 that extends from a bottom portion of the cupsection 12 ₂ in the axial direction, an inner joint member 16 ₂ housedalong an inner periphery of the cup section 12 ₂ of the outer jointmember 11 ₂, and rollers 19 serving as torque transmitting elements thatare arranged between the outer joint member 11 ₂ and the inner jointmember 16 ₂. The inner joint member 16 ₂ comprises a tripod member 17comprising three equiangular leg shafts 18 on which the rollers 19 areexternally fitted.

The inner ring of the support bearing 6 is fixed to the outer peripheralsurface of the long stem section 13, and the outer ring of the supportbearing 6 is fixed to the transmission case with the bracket (notshown). The outer joint member 11 ₂ is supported by the support bearing6 in a freely rotatable manner, and thus the vibration of the outerjoint member 11 ₂ during driving or the like is prevented as much aspossible.

FIG. 26 are partial vertical sectional views for illustrating the outerjoint member 11 ₂. As illustrated in FIG. 26, the outer joint member 11₂ comprises a bottomed cylindrical cup section 12 ₂ that is opened atone end and has inner peripheral surfaces 31 ₂ and the track grooves 30₂, on which the rollers 19 (see FIG. 25) are caused to roll, formed atthree equiangular positions on an inner peripheral surface of the cupsection 12 ₂, and the long stem section 13 that extends from a bottomportion of she cup section 12 ₂ the axial direction and comprises thespline Sp serving as the torque transmit ling coupling portion formed atthe outer periphery of the end portion on the opposite side to the cupsection 12 ₂ side. The outer joint member 11 ₂ is formed by welding thecup member 12 a ₂ and the shaft member 13 a to each other.

As illustrated in FIG. 26, the cup member 12 a ₂ is an integrally-formedproduct having a cylindrical portion 12 a 1 ₂ and a bottom portion 12 a2 ₂. The cylindrical portion 12 a 1 ₂ has the track grooves 30 ₂ and theinner peripheral surfaces 31 ₂ formed at the inner periphery thereof. Aprojecting portion 12 a 3 ₂ is formed at the bottom portion 12 a 2 ₂ ofthe cup member 12 a ₂. The boot mounting groove 32 is formed at an outerperiphery of the cup member 12 a ₂ on the opening side thereof. Thebearing mounting surface 14 and the snap ring groove 15 are formed atthe outer periphery of the shaft member 13 a on the cup member 12 a ₂side, whereas the spline Sp is formed at the end portion on the oppositeside to the cup member 12 a ₂ side.

A joining end surface 50 a formed at the projecting portion 12 a 3 ₂ ofthe bottom portion 12 a 2 ₂ of the cup member 12 a ₂ and the joining endsurface 51 formed at the end portion of the shaft member 13 a on the cupmember 12 a ₂ side are brought into abutment against each other, and arewelded to each other by electron beam welding performed from theradially outer side. The welded portion 49 is formed of a bead formed bya beam radiated from the radially outer side of the cup member 12 a ₂.Similarly to the outer joint member according to the first embodiment,the outer diameters B (B1 and B2) of the joining end surface 50 ₂ andthe joining end surface 51 are set to equal dimensions for each jointsize. The welded portion 49 is formed on the joining end surface 51located on the cup member 12 a ₂ side with respect, to the bearingmounting surface 14 of the shaft member 13 a, and hence the bearingmounting surface 14 and the like can be processed in advance so thatpost-processing, after welding, can be omitted. Further, the electronbeam welding does not cause formation of burrs at the welded portion.Thus, post-processing for the welded portion can also be omitted,thereby being capable of reducing the manufacturing cost.

The outer joint member 11 ₂ is similar to the outer joint memberdescribed in the first embodiment in relation to the manufacturingmethod for the outer joint member 11 described above, and is similarlyapplicable to a second embodiment and a third embodiment of the presentinvention in relation to the manufacturing method for an outer jointmember described above. Therefore, all of those are similarly applied,and redundant description is omitted.

FIG. 27 is an illustration of a manufacturing method according to thesecond embodiment of the present invention. In the manufacturing stepsof the second embodiment, the heat treatment step for the cup member,which is involved in the heat treatment step S7 in FIG. 3 as describedin the first embodiment, is provided before the welding step S6 in thesequence and named “heat treatment step S5 c”, to thereby prepare thecup member as a finished product. Details of other aspects of the secondembodiment than this aspect, that is, details of the overview of therespective steps, the states of the cup member and the shaft member inthe main processing steps, the preparation of the cup member for commonuse, the welding method, the method for the ultrasonic flaw detectioninspection, the standardization of the product type, the configurationof the outer joint member, and the like as described above in connectionwith the manufacturing method according to the first embodiment are thesame as those of the first embodiment. Therefore, all the details of thefirst embodiment are applied in the second embodiment, and only thedifference is described.

As illustrated in FIG. 4b , the cup member 12 a has a shape extendingfrom the joining end surface 50 to the large-diameter cylindricalportion 12 a 1 via the bottom portion 12 a 2, and the portions to besubjected to heat treatment that involves quenching and tempering arethe track grooves 30 and the cylindrical inner peripheral surface 42located at the inner periphery of the cylindrical portion 12 a 1.Therefore, the cup member 12 a generally has no risk of thermal effecton the heat-treated portion during the welding. For this reason, the cupmember 12 a is subjected to heat treatment before the welding to beprepared as a finished component. The manufacturing steps of the secondembodiment are suitable in practical use.

In the manufacturing steps of the second embodiment, the cup member 12 ais subjected to heat treatment for preparing the cup member 12 a as afinished product, and is therefore assigned with a product numberindicating a finished product for management. Thus, the standardizationof the product type of the cup member 12 a remarkably reduces the costand alleviates the burden of production management. Further, the cupmember 12 a can be manufactured solely until the cup member 12 a iscompleted as a finished product through the forging, turning, and heattreatment. Thus, the productivity is enhanced by virtue of reduction ofsetups and the like as well.

In the second embodiment, in FIG. 34 for illustrating the example, ofstandardization of the product type of the cup member as described abovein the first embodiment, only the product number of the cup member inFIG. 24 is changed to the product number indicating a finished product,whereas the product numbers of the shaft, member and the outer jointmember are the same as those of the first embodiment. Therefore,description thereof is omitted herein.

FIG. 28 is an illustration of a manufacturing method, according to thethird embodiment of the present invention. In the manufacturing steps ofthe third embodiment, the heat treatment steps for the cup section andthe shaft section, which are involved in the heat treatment step S7 inFIG. 3 as described above in the first embodiment, and the grinding stepS8 for the shaft section are provided before the welding step S6 in thesequence and named “heat treatment step S5 c for cup member”, “heattreatment step S4 s for shaft member”, and “grinding step S5 s”. Thus,both the cup member and the shaft member are prepared as finishedproducts. Details of other aspects of the third embodiment than thisaspect, that is, details of the overview of the respective steps, thestates of the cup member and the shaft member in the main processingsteps, the preparation of the cup member for common use, the weldingmethod, the method for the ultrasonic flaw detection inspection, thestandardization of the product type, the configuration of the outerjoint member, and the like as described above in connection with themanufacturing method according to the first embodiment are the same asthose of the first embodiment. Therefore, all the details of the firstembodiment are applied in the third embodiment, and only the differenceis described.

After the spline processing step S3 s, a hardened layer having ahardness of approximately from 50 HRC to 62 HRC is formed in apredetermined range of the outer peripheral surface of the shaft memberby induction quenching in the heat treatment step S4 s. Heat treatmentis not performed on a predetermined portion in the axial direction,which includes the joining end surface 51. The heat treatment for thecup member, the assignment of the product number, and the like are thesame as those in the manufacturing method according to the secondembodiment, and redundant description is therefore omitted herein.

After the heat treatment step S4 s, the shaft member is transferred tothe grinding step S5 s so that the bearing mounting surface 14 and thelike are finished. Thus, the shaft member is obtained as a finishedproduct. Then, the shaft member is assigned with a product numberindicating a finished product for management. The manufacturing steps ofthe third embodiment are suitable in a case of a cup member and a shaftmember having shapes and specifications with no risk of thermal effecton the heat-treated portion during the welding.

In the manufacturing steps of the third embodiment, both the cup memberand the shaft member can be assigned with product numbers indicatingfinished products for management. Thus, the standardization of theproduct type of the cup member further remarkably reduces the cost, andalleviates the burden of production management. Further, the cup memberand the shaft member can be manufactured independently of each otheruntil the cup member and the shaft member are completed as finishedproducts through the forging, turning, heat treatment, grinding afterheat treatment, and the like. Thus, the productivity is further enhancedby virtue of reduction of setups and the like as well.

In the third embodiment, in FIG. 24 for illustrating the example ofstandardization of the product type of the cup member as described abovein the first embodiment, the product numbers of the cup member and theshaft member in FIG. 24 are changed to the product numbers indicatingfinished products. The product number of the outer joint member is thesame as that of the first embodiment. Therefore, description thereof isomitted herein. Note that, the cup member and the shaft member to beprepared as finished components are not limited to the cup member andthe shaft member subjected to finishing such as the above-mentionedgrinding after heat treatment or cutting after quenching, but encompassa cup member and a shaft member in a state in which the heat treatmentis completed while the finishing is uncompleted.

As described in the standardization of the product type, the cup memberis not limited to one type for one joint size, that is, not limited toone type assigned with a single product number. Specifically, asdescribed above, the cup member encompasses, for example, cup members ofa plurality of types (assigned with a plurality of product numbers,respectively) that are prepared for one joint size based on differentspecifications of a maximum operating angle, and are also prepared sothat the outer diameters B1 of the above-mentioned joining end surfacesof the cup members are set to equal dimensions. In addition, the cupmember encompasses, for example, cup members of a plurality of types(assigned with a plurality of product numbers, respectively) that areprepared for one joint size in order to achieve management of the cupmembers in a plurality of forms including intermediate components beforeheat treatment and finished components in consideration of the jointfunction, the circumstances at the manufacturing site, the productivity,and the like, and are also prepared so that the outer diameters B1 ofthe above-mentioned joining end surfaces of the cup members are set toequal dimensions.

In the above-mentioned embodiments, the case to which electron beamwelding is applied is described, but laser welding is also similarlyapplicable.

In the outer joint, member according to the embodiments described above,the cases where the present invention is applied to the double-offsettype constant velocity universal joint as the plunging type constantvelocity universal joint 10, and to the tripod type constant velocityuniversal joint 10 ₂ as the plunging type constant velocity universaljoint 10 are described. However, the present invention may be applied toan outer joint member of another plunging type constant velocityuniversal joint such as a cross-groove type constant velocity universaljoint, and to an outer joint member of a fixed type constant velocityuniversal joint. Further, in the above, the present invention is appliedto the outer joint member of the constant velocity universal joint,which is used to construct the drive shaft. However, the presentinvention may be applied to an outer joint member of a constant velocityuniversal joint, which is used to construct a propeller shaft.

The present invention is not limited to the above-mentioned embodiments.As a matter of course, various modifications can be made thereto withoutdeparting from the gist of the present invention. The scope of thepresent invention is defined in Claims, and encompasses equivalentsdescribed in Claims and all changes within the scope of claims.

REFERENCE SIGNS LIST

-   1 drive shaft-   2 intermediate shaft-   3 spline-   4 boot-   5 boot-   6 support bearing-   10 plunging type constant velocity universal joint-   11 outer joint member-   11′ workpiece-   12 cup section-   12 a cup member-   12 a 1 cylindrical portion-   12 a 2 bottom portion-   13 long shaft section-   13 a shaft member-   14 bearing mounting surface-   16 inner joint member-   17 tripod member-   19 torque transmitting element (roller)-   20 fixed type constant velocity universal joint-   21 outer joint member-   22 inner joint member-   23 torque transmitting element (ball)-   24 cage-   30 track groove-   31 inner peripheral surface-   40 track groove-   41 torque transmitting element (ball)-   42 cylindrical, inner peripheral, surface-   49 welded portion-   50 joining end surface-   51 joining end surface-   55 flat smooth surface-   100 welding apparatus-   101 electron gun-   108 case-   109 vacuum pump-   111 sealed space-   120 ultrasonic flaw detection-inspection apparatus-   121 base-   122 water bath-   123 workpiece support-   124 upper center hole guide-   125 rotary drive device-   126 lower center hole guide-   128 drive positioning device-   129 vertical-direction drive positioning device-   130 horizontal-direction drive positioning device-   142 drive cylinder-   143 rotary support member-   145 servomotor-   156 drive cylinder-   160 probe-   161 drive positioning device-   165 drive cylinder-   166 drive cylinder-   167 arm member-   168 gear-   169 electric rotary actuator-   170 gear-   171 rack-   B1 outer diameter-   B2 outer diameter-   D inner diameter-   E inner diameter-   G transmission pulse-   Gr1 reflection echo-   Gr2 reflection echo-   Gr3 reflection echo-   K1 defect-   K2 defect-   K3 defect-   O joint center-   O1 curvature center-   O2 curvature center-   RC circumferential inclination angle (incident angle)-   RC′ refraction angle-   S6 welding step-   S6 j removal processing step-   S6 k ultrasonic flaw detection-inspection step-   X1 threshold value-   X2 threshold value

The invention claimed is:
 1. A manufacturing method for an outer jointmember of a constant velocity universal joint, the outer joint membercomprising: a cup section having track grooves formed in an innerperiphery of the cup section, which are engageable with torquetransmitting elements; and a shaft section formed at a bottom portion ofthe cup section, the outer joint member being constructed by forming thecup section and the shaft section as separate members, and by welding acup member forming the cup section and a shaft member forming the shaftsection to each other, the manufacturing method at least comprising: awelding step of welding the cup member and the shaft member to form aworkpiece by irradiating a beam to joining end portions of the cupmember and the shaft member; a removal processing step of causing anouter surface of the workpiece including a welded portion formed in thewelding step to be formed into a cylindrical smooth surface having asurface roughness of Ra 2.0 μm or less by turning; and an ultrasonicflaw detection-inspection step of inspecting the welded portion, theultrasonic flaw detection-inspection step comprising a circumferentialangle beam flaw detection method that includes irradiating ultrasonicwaves to the cylindrical smooth surface of the welded portion with oneprobe in a direction parallel to turning marks formed by the turning andat an incident angle which prevents total reflection of the ultrasonicwaves, wherein the circumferential angle beam flaw detection methodincludes a plurality of steps each of which comprises positioning theone probe in an X-axis direction that is perpendicular to apredetermined diameter line in a cross section of the workpieceperpendicular to an axis of the workpiece, in a Y-axis direction that isparallel to the predetermined diameter line and in a Z-axis directionthat is parallel to the axis of the workpiece while making an axis of anultrasonic transmission pulse to be transmitted from the one probeperpendicular to the predetermined diameter line and offset in theY-axis direction with respect to a longitudinal section of the workpieceincluding the axis of the workpiece, transmitting the ultrasonictransmission pulse from the one probe to the workpiece, and receiving areflection echo from the workpiece, wherein, in the plurality of stepsof the circumferential angle beam flaw detection method, a position ofthe one probe in the Z-axis direction is different in each of theplurality of steps, and the circumferential angle beam flaw detectionmethod further includes repeating the plurality of steps a pluralitytimes, and changing a position of the one probe in the X-axis directionso as to set a focal point of the ultrasonic waves of the one probe to adifferent position within a thickness of the welded portion each of theplurality of times the plurality of steps is performed to therebyinspect an entire region of the welded portion.
 2. The manufacturingmethod for an outer joint member of a constant velocity universal jointaccording to claim 1, wherein the incident angle of the axis of theultrasonic transmission pulse of the ultrasonic waves is set to from 10°to 27°.
 3. The manufacturing method for an outer joint member of aconstant velocity universal joint according to claim 1, wherein thepositioning of the one probe is controlled by a program.
 4. Themanufacturing method for an outer joint member of a constant velocityuniversal joint according to claim 1, wherein the ultrasonic flawdetection-inspection, step further includes rotating the workpieceduring the inspecting.
 5. An ultrasonic flaw detection-inspection methodfor a welded portion of an outer joint member of a constant velocityuniversal joint, the outer joint member comprising: a cup section havingtrack grooves formed in an inner periphery of the cup section, which areengageable with torque transmitting elements; and a shaft section formedat a bottom portion of the cup section, the outer joint member beingconstructed by forming the cup section and the shaft section as separatemembers, and by welding a cup member forming the cup section and a shaftmember forming the shaft section to each other to form a workpiece, theultrasonic flaw detection-inspection method comprising: forming an outersurface of the workpiece including the welded portion into a cylindricalsmooth surface having a surface roughness of Ra 2.0 μm or less byturning; and carrying out a circumferential angle beam flaw detectionmethod including irradiating ultrasonic waves to the cylindrical smoothsurface of the welded portion with one probe in a direction parallel toturning marks formed by the turning and at an incident angle whichprevents total reflection of the ultrasonic waves, wherein thecircumferential angle beam flaw detection method including a pluralityof steps each of which comprises positioning the one probe in an X-axisdirection that is perpendicular to a predetermined diameter line in across section of the workpiece perpendicular to an axis of theworkpiece, in a Y-axis direction that is parallel to the predetermineddiameter line and in a Z-axis direction that is parallel to the axis ofthe workpiece while making an axis of an ultrasonic transmission pulseto be transmitted from the one probe perpendicular to the predetermineddiameter line and offset in the Y-axis direction with respect to alongitudinal section of the workpiece including the axis of theworkpiece, transmitting the ultrasonic transmission pulse from the oneprobe to the workpiece and receiving a reflection echo from theworkpiece, wherein, in the plurality of steps of the circumferentialangle beam flaw detection method, a position of the one probe in theZ-axis direction is different in each of the plurality of steps, and thecircumferential angle beam flaw detection method further includesrepeating the plurality of steps a plurality times, and changing aposition of the one probe in the X-axis direction so as to set a focalpoint of the ultrasonic waves of the one probe to a different positionwithin a thickness of the welded portion each of the plurality of timesthe plurality of steps is performed to thereby inspect an entire regionof the welded portion.